title: Pharmacokinetics of intravenous and intramuscular buprenorphine in the horse.
abstract: The purpose of this study was to determine the pharmacokinetics of buprenorphine following intravenous (i.v.) and intramuscular (i.m.) administration in horses. Six horses received i.v. or i.m. buprenorphine (0.005 mg/kg) in a randomized, crossover design. Plasma samples were collected at predetermined times and horses were monitored for adverse reactions. Buprenorphine concentrations were measured using ultra-performance liquid chromatography with electrospray ionization mass spectrometry. Following i.v. administration, clearance was 7.97±5.16 mL/kg/min, and half-life (T(1/2)) was 3.58 h (harmonic mean). Volume of distribution was 3.01±1.69 L/kg. Following i.m. administration, maximum concentration (C(max)) was 1.74±0.09 ng/mL, which was significantly lower than the highest measured concentration (4.34±1.22 ng/mL) after i.v. administration (P<0.001). Time to C(max) was 0.9±0.69 h and T(1/2) was 4.24 h. Bioavailability was variable (51-88%). Several horses showed signs of excitement. Gut sounds were decreased 10±2.19 and 8.67±1.63 h in the i.v. and i.m. group, respectively. Buprenorphine has a moderate T(1/2) in the horse and was detected at concentrations expected to be therapeutic in other species after i.v. and i.m. administration of 0.005 mg/kg. Signs of excitement and gastrointestinal stasis may be noted.
authors.affiliation: Department of Clinical Sciences, North Carolina State University, College of Veterinary Medicine, Raleigh, NC 27606, USA. jennifer_davis@ncsu.edu
authors.forename: J L
authors.initials: JL
authors.lastname: Davis
authors.forename: K M
authors.initials: KM
authors.lastname: Messenger
authors.forename: D H
authors.initials: DH
authors.lastname: LaFevers
authors.forename: B M
authors.initials: BM
authors.lastname: Barlow
authors.forename: L P
authors.initials: LP
authors.lastname: Posner
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000818:Animals; D019540:Area Under Curve; D002047:Buprenorphine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D005260:Female; D006207:Half-Life; D006736:Horses / Q000097:blood / Q000378:metabolism*; D007273:Injections, Intramuscular; D007275:Injections, Intravenous; D008297:Male
chemical_list: D000701:Analgesics, Opioid; D002047:Buprenorphine